Polycarboxylic acid derivatives and uses

ABSTRACT

Mercapto polycarboxylic acids, especially the trithiocarbonate derivatives thereof and alkali metal salts, are employed as treating agents in mineral recovery operations.

BACKGROUND OF THE INVENTION

This application is a division of Ser. No. 480,206 filed Mar. 30, 1983now U.S. Pat. No. 4,482,480.

The present invention relates to a composition of matter. In anotheraspect, the invention relates to a depressant composition useful in oreflotation operations. Another aspect of this invention relates to aprocess for recovering minerals from ore compositions. Yet a furtheraspect of this invention relates to a process for preparing acomposition of matter.

Flotation processes are known in the art and are used for recovering andconcentrating minerals from ores. In froth flotation processes the oreis crushed and wet ground to obtain a pulp. Additives such as mineralflotation or collecting agents, frothers, suppressants, stabilizers,etc. are added to the pulp to assist separating valuable materials fromundesirable or gangue portions of the ore in subsequent flotation steps.The pulp is then aerated to produce a froth at the surface. The mineralswhich adhere to the bubbles or froth are skimmed or otherwise removedand the mineral bearing froth is collected and further processed toobtain the desired minerals. Typical mineral flotation collectorsinclude xanthates, amines, alkyl sulfates, arene sulfonates,dithiocarbamates, dithiophosphates, and thiols.

While the art of ore flotation has reached a significant degree ofsophistication it is a continuing goal in the ore flotation industry toincrease the productivity of ore flotation processes and above all toprovide specific processes which are selective to one ore or to onemetal over other ores or other metals, respectively, which are presentin the material to be treated.

OBJECTS OF THE INVENTION

It is one object of this invention to provide a composition useful inore flotation processes.

Another object of this invention is to provide a process to produce sucha composition.

Yet a further object of this invention is to provide an improvedflotation process using the new depressant composition.

A still further object of this invention is to provide an improvedmolybdenum flotation process in which less iron, copper and lead ispresent in the molybdenum values recovered.

These and other objects, advantages, details, features and embodimentsof this invention will become apparent to those skilled in the art fromthe following detailed description of the invention and the appendedclaims.

SUMMARY OF THE INVENTION

In one aspect, the invention relates to a composition which comprises anammonium or Group IA metal salt of the trithiocarbonate derivative of amercapto polycarboxylic acid, said salt being represented by theformula: ##STR1## where M represents ammonium or Group IA metal and Arepresents ##STR2## R₁ and R₂ are selected from the group consisting ofhydrogen and an alkyl group having 1 to 3 carbon atoms, R₃ is selectedfrom the group consisting of hydrogen, alkyl group having 1 to 3 carbonatoms, and COOM and x and y are 0 or an integer of 1 through about 7.

In another aspect, a composition is prepared by reacting an ammonium orGroup IA metal salt of a mercapto polycarboxylic acid which can berepresented by the above formula where A equals M, with carbondisulfide, CS₂. The ammonium or Group IA metal salt of the mercaptopolycarboxylic acid can be prepared by neutralizing a mercaptopolycarboxylic acid which can be represented by the above formula whereA and M are both hydrogen with ammonium hydroxide or alkali metalhydroxide.

In yet another aspect of the invention, it has been found thatcompositions represented by the formula: ##STR3## where M representshydrogen, ammonium or Group IA metal, A represents hydrogen, ammonium,Group IA metal, or ##STR4## R₁ and R₂ are selected from the groupconsisting of hydrogen, alkyl group having 1 to 3 carbon atoms; R₃ isselected from the group consisting of hydrogen, alkyl group having 1 to3 carbon atoms and COOM; and x and y are 0 or an integer of 1 throughabout 7, are usefully employed as treating agents in a minerals recoveryoperation, especially a molybdenum flotation operation.

DETAILED DESCRIPTION OF THE INVENTION

The composition of matter of the present invention comprises an ammoniumor Group IA metal salt of the trithiocarbonate derivative of a mercaptopolycarboxylic acid, preferably a dicarboxylic acid. This salt can berepresented by the formula: ##STR5## where M represents ammonium orGroup IA metal, and A represents ##STR6## R₁ and R₂ are selected fromthe group consisting of hydrogen and an alkyl group having 1 to 3 carbonatoms, R₃ is selected from the group consisting of hydrogen, alkyl grouphaving 1 to 3 carbon atoms, and COOM, and x and y are 0 or an integer of1 through about 7. Suitable Group IA metals for forming the salt arealkali metals, such as lithium, sodium, potassium, rubidium, and cesium.Sodium is the preferable Group IA alkali metal with which to form thesalt.

The above described compositions can be prepared by reacting an ammoniumor Group IA metal salt of a mercapto polycarboxylic acid which can berepresented by the above formula except that A is M, with carbondisulfide, CS₂. The ammonium or Group IA metal salt of the mercaptopolycarboxylic acid can be prepared by neutralizing a mercaptopolycarboxylic acid which can be represented by the above formula exceptthat A and M are hydrogen with ammonium hydroxide or alkali metalhydroxide. Suitable mercapto polycarboxylic acid starting materials aremercaptomalonic acid, 2-mercaptoglutaric acid, 2-mercaptosebacic acid,mercaptosuccinic acid, 3-mercaptoadipic acid, 3-mercaptocitric acid andcombinations of these. Of these, mercaptosuccinic acid is the preferredstarting material since it is commercially available and has been usedwith good results. Generally, aqueous sodium hydroxide is employed toneutralize the mercapto carboxylic acid. To the neutralized solution,the carbon disulfide is added in an amount sufficient to result in thetreating agent.

The aqueous treating agent thus obtained is the preferred treating agentof the invention for use as a depressant composition in a flotationprocess.

Generally, the flotation process comprises carrying out a mineralsflotation with a depressant composition present, with the depressantcomposition being represented by the formula: ##STR7## where Mrepresents hydrogen, ammonium, or Group IA metal, A represents hydrogen,ammonium, Group IA metal, ##STR8## R₁ and R₂ are selected from the groupconsisting of hydrogen, alkyl group having 1 to 3 carbon atoms; R₃ isselected from the group consisting of hydrogen, alkyl group having 1 to3 carbon atoms, and COOM; and x and y are 0 or an integer of 1 throughabout 7. Preferably, A is represented by the formula ##STR9## Morepreferably, A is represented by the formula ##STR10## and M is sodium.Even more preferably, the compositions represented by the above formulahave been derived from mercaptomalonic acid, 2-mercaptoglutaric acid,2-mercaptosebacic acid, mercaptosuccinic acid, 3-mercaptoadipic acid, or3-mercaptocitric acid.

Generally, the flotation process will utilize a composition comprisingthe mercapto polycarboxylic acid or derivative, water, and the mineralmaterial. The depressants of the present invention can be used todepress iron, copper and/or lead in the presence of molybdenum. Usuallythe metals are in solid sulfided form and form a slurry, which can befinely divided, as in a pulp. For example, the invention can be employedto process an ore slurry containing high copper values. The inventioncan also be employed to process a concentrate, such as a concentratewhich contains high molybdenum values. Generally, the solids to beprocessed will be present as a slurry in water which contains themercapto polycarboxylic acid or derivative with the mercaptopolycarboxylic acid or derivative being present in an amount of betweenabout 0.005 and about 20 pounds per ton of the solids. The slurryusually contains between about 10 and 75 weight percent solidspreferably in the range of 15-60 weight percent solids, depending on theprocessing stage. Preferably, the mercapto polycarboxylic acid orderivative is present in the composition in an amount in the range ofbetween about 0.01 to about 6 pounds per ton of solids. Even morepreferably, the mercapto polycarboxylic acid or derivative is present inan amount in the range of between about 0.5 and about 4 pounds per tonof the solids.

The flotation process usually involves the steps of:

(a) mixing crushed or ground mineral material with water and thedepressant defined above to establish a pulp,

(b) aerating the pulp to produce a froth and a pulp,

(c) separating the froth from the pulp and producing a concentrateproduct and a tail product,

(d) recovering minerals from the so separated concentrate and/or tailproduct.

The suppressant composition of the invention can also be employed withfrothers and flotation agents.

Examples of frothers that can be used in addition to the collectorcompositions defined above are polyoxyalkylene glycols and theircorresponding methyl or ethyl ethers having broadly a molecular weightof about 400 to about 1000, and preferably a molecular weight in therange of about 420 to about 780. Particularly polypropylene glycols andtheir ethers having molecular weights of e.g., 400, 425, 750 or 900 canbe used. Also polybutylene glycol and polypentylene glycol are usefulmaterials. Examples of other frothers that may be used are alcohols suchas methyl isobutyl carbinol, pine oil, phenols, fatty acids and cresylicacid. Examples of suitable flotation agents are organic xanthates,organic trithiocarbonates, amines, dithiocarbamates, fuel oils, aromaticoils and the like, generally in an amount of 0.005-0.5 pounds per ton ofsolids. Preferably frother and an oily flotation agent are usedtogether.

The inventive suppressants can be used together with other suppressantsor suppression steps if desired. For example, the suppressantcomposition defined above can be used after a surface treatment of thesolids, such as after heating or oxidation of a concentrate or withsulfuric acid, and/or with additional suppressants, such as sodiumcyanide, sodium ferrocyanide, lime and zinc sulfate, in the treatment ofan ore.

The present invention is applicable to a variety of ores. The inventionis particularly suitable for sulfided ores. Among the sulfided ores themolybdenum bearing ores and especially the molybdenum bearing ores whichalso contain copper, iron, or lead impurities, especially impurities ofthese metals in the sulfided form, are preferred. Examples of molybdenumbearing ores which are usefully processed with this invention are

    ______________________________________                                        Molybdenite        MoS.sub.2                                                  Wulfenite          PbMoO.sub.4                                                Porwellite         Ca(Mo,W)O.sub.4                                            Ferrimolybdite     Fe.sub.2 Mo.sub.3 O.sub.12.8H.sub.2 O.                     ______________________________________                                    

Examples of copper ores which can be processed using inventivecompositions, and/or which yield concentrates which can be processedusing inventive compositions include

    ______________________________________                                        Chalcocite        Cu.sub.2 S                                                  Chalcopyrite      CuFeS.sub.2                                                 Covallite         CuS                                                         Bornite           Cu.sub.5 FeS.sub.4                                          Cubanite          Cu.sub.2 SFE.sub.4 S.sub.5                                  Valerite          Cu.sub.2 Fe.sub.4 S.sub.7 or Cu.sub.3 Fe.sub.4 S.sub.7      Enargite          Cu.sub.3 (As,Sb)S.sub.4                                     Tetrahedrite      Cu.sub.3 SbS.sub.2                                          Tennanite         Cu.sub.12 As.sub.4 S.sub.13                                 ______________________________________                                    

The following examples further illustrate preferred embodiments of thisinvention.

EXAMPLE I

This example describes the preparation of inventive collectors namely,disodium mercaptosuccinate and trisodium succinyl trithiocarbonate. To a3-neck glass flask fitted with a condenser, stirrer, thermometer anddropping funnel was added 125 milliliters of water and 42 grams (1.05moles) of sodium hydroxide. After cooling to below 50° C., 50 grams(0.33 mole) of mercaptosuccinic acid was slowly added with stirring overa 20 minute period. The mixture was cooled to below 45° C. whereupon25.4 grams (0.333 mole) of carbon disulfide was slowly added over a 30minute period. The cloudy mixture was maintained with stirring at 45° C.for about 1.5 hours and the solution became clear and orange-colored.The solution was cooled to room temperature and bottled. The solutionwas calculated to be 40 weight percent of trisodium succinyltrithiocarbonate. The disodium salt of mercaptosuccinic acid solutiondisclosed herein was comprised of 1 gram of the free acid, 5 millilitersof 5 weight percent NaOH and 94 milliliters of H₂ O.

EXAMPLE II

This example discloses the use of mercaptosuccinic acid derivativesdescribed in Example I as ore flotation reagents, particularly as a Cu,Fe and Pb suppressant in a Mo ore flotation process. To a ball mill waschrged 2010 grams of a Mo-bearing ore from Cyprus-Thompson Creek Minesalong with 1000 milliliters of water, 0.5 g (0.5 lb/ton) lime and 5milliliters (0.05 lb/ton) of a 1 weight percent aqueous solution ofdisodium mercaptosuccinate. Also added was 0.2 lb/ton (31 drops) of afuel oil. The mixture was ground for 27.5 minutes, transferred to aDenver D-12 flotation cell along with enough water to come within 1 inchof the cell lip (approximately 30 percent solids). Also added to thecell was 15 drops (0.08 lb/ton) of a frother, MIBC (methyl isobutylcarbinol) and enough lime to adjust the pH to 8.9. The slurry wasconditioned for 1 minute at 1500 rpm and floated for 1 minute. Therougher concentrate was filtered, dried analyzed. The run was repeatedwhereupon the average weight percent recovery of Mo, Cu, Fe and Pb wasrespectively 97.5%, 36.7%, 2.4% and 9.0%.

Several controls were then evaluated and the results compared with theinventive runs (No. 5). These results are all listed in Table I where itcan be seen that the disodium mercaptosuccinate is a better suppressant(gives a lower % recovery) of Cu, Fe and Pb than any of the controls,Runs 1, 2, 3 and 4. Runs 2 and 3 employed similar compounds to theinventive compound except they were based on a monocarboxylic acid thioderivative rather than a dicarboxylic acid thio derivative. Likewise,Runs 1 and 2 are suppressants which did not perform as effectively as aCu, Fe or Pb suppressant as the inventive run. The inventive suppressantcontinued to give about the same Mo recovery as the controls.

EXAMPLE III

This example discloses the effectiveness of both disodiummercaptosuccinate and trisodium succinyl trithiocarbonate as a Cu and Fesuppressant in a Cu ore concentrate. The general flotation processdescribed in Example II was again followed but this time a Cu oreconcentrate (Anamax Mines) was used instead of the ore itself, thus, nogrind stage was carried out. The concentrate, about 415 milliliters (600grams solids) of pulp (69 wt. % solids) was added to a 3-Liter AgitarLA500 flotation cell. After the suppressant was added and conditionedfor 1-2 minutes the mineral was floated for 5 minutes at 200 rpm at anatural pH of 10.4. The new concentrate was filtered, dried andanalyzed. The run was again repeated but the pH was adjusted to 6.4 withconcentrated H₂ SO₄ before floating. These results of both the inventiveruns and controls are listed in Table II where it can be seen that theinventive suppressants, Runs 4 and 5, result in low recoveries of Fe andCu while maintaining higher recoveries of Mo, hence, a higher purity ofMo is obtained with these suppressants as compared with the controls,Runs 1, 2 and 3. The two inventive suppressants, Runs 4 and 5, operateat both acidic and basic conditions giving low Cu and Fe recoverieswhile maintaining high Mo recoveries. Of the two inventive materials,trisodium succinyl trithiocarbonate appears to give the best Fe and Cusuppressant values.

                                      TABLE I                                     __________________________________________________________________________    Effect of Mercaptoalkanoic Acids as                                           Cu, Fe, Pb Suppressants in a Mo Ore Flotation Process                         2010 grams Ore (Cyprus-Thompson Creek)                                        Run                  Rougher Concentrate,                                                                     Wt. % of Recovery                             No.                                                                              Reagent.sup.a     Total Wt. g                                                                              Mo Cu Fe Pb                                   __________________________________________________________________________    Control:                                                                      1  Na.sub.2 SO.sub.3                                                                          0.25 lb/T                                                                          17.9       98.1                                                                             59.7                                                                             4.33                                                                             26.5                                                      17.6       98.0                                                                             50.9                                                                             2.68                                                                             28.3                                                      Average =  98.1                                                                             55.3                                                                             3.51                                                                             27.40                                2  Sodium Thioglycolate                                                                       0.50 lb/T                                                                          20.2       97.3                                                                             46.7                                                                             2.91                                                                             32.9                                                      18.0       97.6                                                                             43.0                                                                             2.74                                                                             6.14                                                      Average =  97.5                                                                             44.9                                                                             2.83                                                                             19.52                                3  Sodium Thiolactate                                                                         0.50 lb/T                                                                          22.3       98.1                                                                             50.6                                                                             3.24                                                                             32.3                                                      19.6       97.2                                                                             47.7                                                                             2.67                                                                             27.0                                                      Average =  97.7                                                                             49.2                                                                             3.00                                                                             29.7                                 4  Disodium Carboxymethyl                                                                     0.50 lb/T                                                                          16.7       97.7                                                                             55.6                                                                             3.12                                                                             31.6                                    Trithiocarbonate, .sup.b                                                                        19.7       97.9                                                                             54.8                                                                             3.34                                                                             31.6                                                      Average =  97.8                                                                             55.2                                                                             3.23                                                                             31.6                                  Invention:                                                                   5  Disodium Mercapto-                                                                         0.50 lb/T                                                                          17.3       97.3                                                                             32.1                                                                             2.47                                                                             13.5                                    Succinate         18.7       97.7                                                                             41.3                                                                             2.42                                                                             4.52                                                      Average =  97.5                                                                             36.7                                                                             2.44                                                                             9.01                                 __________________________________________________________________________     .sup.a 1 wt. % Aq. Solution                                                   .sup.b Available from Phillips Petroleum Co., ORFOM D8                   

                                      TABLE II                                    __________________________________________________________________________    Effect of Mercapto Succinic Acid Salts as                                     Suppressants in a Mo Flotation Process                                        415 mL (600 g solids) Cu Ore Concentrate (Anamax Mines)                                          pH 6.4          pH 10.4                                    Run                Concentrate,                                                                         Wt. % Recovery                                                                         Concentrate,                                                                         Wt. % Recovery                      No.                                                                              Suppressant - lb/Ton                                                                          Wt., g Cu Fe Mo Wt., g Cu Fe Mo                            __________________________________________________________________________    Control:                                                                      1  None         -- 33.9   5.1                                                                              4.3                                                                              82.5                                                                             142    25.7                                                                             25.7                                                                             27.8                          2  Molyflo.sup.a                                                                              0.14                                                                             41.3   6.3                                                                              5.3                                                                              84.8                                                                             165    28.5                                                                             28.2                                                                             32.7                          3  Disodium Carboxymethyl                                                                     0.8                                                                              25.0   3.0                                                                              4.0                                                                              6.3                                                                              26.2   3.4                                                                              4.0                                                                              57.9                             Trithiocarbonate.sup.b                                                     Invention:                                                                    4  Disodium Mercapto-                                                                         0.8                                                                              35.8   5.1                                                                              4.3                                                                              75.8                                                                             86.6   16.6                                                                             13.1                                                                             66.9                             succinate                                                                  5  Trisodium Succinyl                                                                         0.8                                                                              24.3   2.8                                                                              3.3                                                                              78.5                                                                             24.9   3.0                                                                              3.2                                                                              72.1                             Trithiocarbonate                                                           __________________________________________________________________________     .sup.a A Mo collector based on a hydrocarbon oil, available from Phillips     Petroleum Co.                                                                 .sup.b A suppressant, ORFOM D8, available from Phillips Petroleum Co.    

What is claimed is:
 1. A process for depressing sulfides of at least oneof copper, iron and lead in a minerals containing mixture in a flotationoperation, said process comprising carrying out a flotation with adepressant composition present, said depressant composition comprising amercapto polycarboxylic acid or derivative represented by the formula:##STR11## where R₁ and R₂ are selected from the group consisting ofhydrogen and an alkyl group having 1 to 3 carbon atoms and R₃ isselected from the group consisting of hydrogen, alkyl group having 1-3carbon atoms and COOM,M is selected from the group consisting ofhydrogen, ammonium, Li, Na, K, Rb and Cs, A is selected from the groupconsisting of M and ##STR12## and where x and y are 0 or any integerfrom 1 through
 7. 2. Process in accordance with claim 1 wherein saidminerals to be depressed comprise sulfided minerals.
 3. Process inaccordance with claim 2 wherein the depressant composition comprises anammonium or Group IA metal salt of a mercapto polycarboxylic acidselected from the group consisting of mercaptomalonic acid,2-mercaptoglutaric acid, 2-mercaptosebacic acid, mercaptosuccinic acid,3-mercaptoadipic acid, 3-mecaptocitric acid and the trithiocarbonatederivative of one of these mercapto polycarboxylic acid salts.
 4. Aprocess as in claim 3 further comprising recovering amolybdenum-containing mineral by flotation.
 5. In a process for therecovery of molybdenum values from an ore containing molybdenum, whereinthe values are recovered in a froth from an aqueous slurry containingthe ore or a concentrate from the ore, wherein the slurry furthercontains sulfides of at least one of copper, iron and lead, theimprovement comprising employing in the aqueous slurry at least onedepressant represented by the formula: ##STR13## where R₁ and R₂ areselected from the group consisting of hydrogen and an alkyl group having1 to 3 carbon atoms and R₃ is selected from the group consisting ofhydrogen, alkyl group having 1-3 carbon atoms and COOM, M is selectedfrom the group consisting of hydrogen, ammonium, Li, Na, K, Rb and Cs, Ais selected from the group consisting of M and ##STR14## and x and y are0 or any integer from 1 through
 7. 6. A process as in claim 5 whereinthe depressant comprises an ammonium or Group IA metal salt of amercaptopolycarboxylic acid selected from the group consisting ofmercaptomalonic acid, 2-mercaptoglutaric acid, 2-mercaptosebacic acid,mercaptosuccinic acid, 3-mercaptoadipic acid, 3-mercaptocitric acid anda trithiocarbonate derivative of one of said acids.
 7. A process as inclaim 6 wherein the depressant is employed in the range of 0.01 to about10 pounds per ton of ore or concentrate.
 8. The process as in claim 7wherein the depressant comprises a sodium salt of the trithiocarbonatederivative of the mercaptopolycarboxylic acid.
 9. A process as in claim8 wherein the depressant comprises a sodium salt of mercaptosuccinicacid.
 10. A process as in claim 7 wherein the depressant comprises thesodium salt of the mercapto polycarboxylic acid or trithiocarbonatederivative thereof.
 11. A process as in claim 10 wherein the depressantcomprises a sodium salt of the trithiocarbonate derivative of succinicacid.